The present invention relates to luminaires generally; it particularly relates to ceiling mounted, wall mounted, furniture mounted, suspended, or free standing luminaires having light passing media, such as light directing lenses or non-directional diffusers, wherein the media is normally seen by persons in the vicinity of the fixture.
Fluorescent luminaires of the type frequently used in office and commercial environments are characterized by a linear geometry, that is, they are elongated fixtures with a uniform cross-sectional shape. Such fixtures are commonly fabricated of steel or extruded aluminum parts, and commonly use elongated, linear plastic lenses or diffusers to mask or control light emitted from the bare fluorescent lamps. Prismatic lenses, which act to converge, diverge, or redirect light, and diffusers, which are translucent, non-directional media that pass light in a cosine distribution, have been used in direct lighting fixtures for many years. More recently lenses, and particularly linear prismatic lenses, have been adapted for use in indirect lighting fixtures where the light source is normally masked by the fixture housing itself. In the case of indirect fixtures, lenses, such as disclosed in co-pending application Ser. No. 046,970, achieve desirable indirect light distributions and are used to eliminate bright spots on wall and ceiling surfaces. They also permit the lamps to be raised within the housing for increased luminaire efficiency.
In the case of both the direct, indirect, and direct-indirect fixtures, all or a portion of the lens or diffuser surface will be seen by persons standing in view of the fixtures. The diffuser will appear as a plain white surface. The prismatic lens will, up close, display a lens pattern characterized by alternating areas of relative brightness and darkness, but further away the prismatic lens pattern will become less perceptible. The prismatic lens presents special problems in terms of visual comfort in that overly bright areas often appear at individual prism surfaces and/or along the base of the lens. Apart from these possible bright spots, the surface of a conventional prismatic lens, like that of a diffuser, appears as a substantially flat, illuminated surface with no distinguishing characteristics.
In the present invention the fixture's light passing media, be it a prismatic lens or a diffuser, is provided with unique visual characteristics at the light emitting surface of the media. The invention is intended to improve visual comfort of a fixture and permit a lighting designer to create different psychological environments through the design of the light passing media. The invention also provides, in a prismatic lens, a lens media wherein surface bright spots can be masked out.